Casein haplotypes and their association with milk production traits in Norwegian Red cattle

• Main Authors: Nome Torfinn, Svendsen Morten, Sehested Erling, Hayes Ben, Olsen Hanne, Nilsen Heidi, Meuwissen Theo, Lien Sigbjørn
• Format: Article
• Language: deu
• Published: BMC 2009-02-01
• Series: Genetics Selection Evolution
• Online Access: http://www.gsejournal.org/content/41/1/24

<p>Abstract</p> <p>A high resolution SNP map was constructed for the bovine casein region to identify haplotype structures and study associations with milk traits in Norwegian Red cattle. Our analyses suggest separation of the casein cluster into two haplotype blocks, one consisting of the <it>CSN1S1</it>, <it>CSN2 </it>and <it>CSN1S2 </it>genes and another one consisting of the <it>CSN3 </it>gene. Highly significant associations with both protein and milk yield were found for both single SNPs and haplotypes within the <it>CSN1S1-CSN2-CSN1S2 </it>haplotype block. In contrast, no significant association was found for single SNPs or haplotypes within the <it>CSN3 </it>block. Our results point towards <it>CSN2 </it>and <it>CSN1S2 </it>as the most likely loci harbouring the underlying causative DNA variation. In our study, the most significant results were found for the SNP <it>CSN2_67 </it>with the C allele consistently associated with both higher protein and milk yields. <it>CSN2_67 </it>calls a C to an A substitution at codon 67 in β-casein gene resulting in histidine replacing proline in the amino acid sequence. This polymorphism determines the protein variants A1/B (<it>CSN2_67 </it>A allele) versus A2/A3 (<it>CSN2_67 </it>C allele). Other studies have suggested that a high consumption of A1/B milk may affect human health by increasing the risk of diabetes and heart diseases. Altogether these results argue for an increase in the frequency of the <it>CSN2_67 </it>C allele or haplotypes containing this allele in the Norwegian Red cattle population by selective breeding.</p>